The Experts below are selected from a list of 225 Experts worldwide ranked by ideXlab platform
Tamis Darbre - One of the best experts on this subject based on the ideXlab platform.
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Prebiotic carbohydrate synthesis: zinc–proline catalyzes direct aqueous aldol reactions of α-hydroxy aldehydes and ketones
Organic & biomolecular chemistry, 2005Co-Authors: Jacob Kofoed, Jean-louis Reymond, Tamis DarbreAbstract:Zn–proline catalyzed aldolisation of glycoladehyde gave mainly Tetroses whereas in the cross-aldolisation of glycoladehyde and rac-glyceraldehyde, pentoses accounted for 60% of the sugars formed with 20% of ribose.
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Zinc–proline catalyzed pathway for the formation of sugars
Chemical communications (Cambridge England), 2004Co-Authors: Jacob Kofoed, Jean-louis Reymond, Miguel Machuqueiro, Tamis DarbreAbstract:Zn-proline catalyzes the aldolisation of unprotected glycolaldehyde in water to give Tetroses and hexoses; threose (33% of the product mixture) was formed with 10% enantiomeric excess of the D-isomer.
Laurence Hecquet - One of the best experts on this subject based on the ideXlab platform.
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Evolved Thermostable Transketolase for Stereoselective Two-Carbon Elongation of Non-Phosphorylated Aldoses to Naturally Rare Ketoses
ACS Catalysis, 2019Co-Authors: Marion Lorillière, Romain Dumoulin, Mélanie L’enfant, Agnès Rambourdin, Vincent Théry, Lionel Nauton, Wolf-dieter Fessner, Franck Charmantray, Laurence HecquetAbstract:We propose an ecofriendly, efficient, stereoselective procedure for the two-carbon elongation of nonphosphorylated aldoses (C4–C6) to the corresponding Cn+2 ketoses (C6–C8) in one step, using hydroxypyruvate (HPA) as a ketol donor substrate and an evolved thermostable transketolase from Geobacillus stearothermophilus (TKgst) as a biocatalyst. Simultaneous site saturation mutagenesis (SSM) at two or three key positions in the TKgst active site yielded efficient variants, L382F/F435Y, R521Y/S385/H462N, and R521V/S385D/H462S, with increased activity compared to wild-type TKgst for conversion of two Tetroses (d-threose, l-erythrose), two pentoses (d-xylose, d-ribose), and two hexoses (d-allose, d-glucose), respectively. These six Cn aldoses as acceptor and HPA as donor substrates were transformed by the TKgst variants at 60 °C with practically complete conversion. The corresponding Cn+2 ketoses, including two hexuloses (d-tagatose, l-psicose), two heptuloses (d-altro-heptulose, d-ido-heptulose), and two octuloses (d-glycero-d-ido-octulose, d-glycero-d-altro-octulose) are naturally rare compounds with important biological functions, which were obtained with high diastereoselectivity.
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Evolved Thermostable Transketolase for Stereoselective Two-Carbon Elongation of Non-Phosphorylated Aldoses to Naturally Rare Ketoses
ACS Catalysis, 2019Co-Authors: Marion Lorillière, Romain Dumoulin, Mélanie L’enfant, Agnès Rambourdin, Vincent Théry, Lionel Nauton, Wolf-dieter Fessner, Franck Charmantray, Laurence HecquetAbstract:We propose an ecofriendly, efficient, stereoselective procedure for the two-carbon elongation of nonphosphorylated aldoses (C4–C6) to the corresponding Cn+2 ketoses (C6–C8) in one step, using hydroxypyruvate (HPA) as a ketol donor substrate and an evolved thermostable transketolase from Geobacillus stearothermophilus (TKgst) as a biocatalyst. Simultaneous site saturation mutagenesis (SSM) at two or three key positions in the TKgst active site yielded efficient variants, L382F/F435Y, R521Y/S385/H462N, and R521V/S385D/H462S, with increased activity compared to wild-type TKgst for conversion of two Tetroses (d-threose, l-erythrose), two pentoses (d-xylose, d-ribose), and two hexoses (d-allose, d-glucose), respectively. These six Cn aldoses as acceptor and HPA as donor substrates were transformed by the TKgst variants at 60 °C with practically complete conversion. The corresponding Cn+2 ketoses, including two hexuloses (d-tagatose, l-psicose), two heptuloses (d-altro-heptulose, d-ido-heptulose), and two octul...
Jacob Kofoed - One of the best experts on this subject based on the ideXlab platform.
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Prebiotic carbohydrate synthesis: zinc–proline catalyzes direct aqueous aldol reactions of α-hydroxy aldehydes and ketones
Organic & biomolecular chemistry, 2005Co-Authors: Jacob Kofoed, Jean-louis Reymond, Tamis DarbreAbstract:Zn–proline catalyzed aldolisation of glycoladehyde gave mainly Tetroses whereas in the cross-aldolisation of glycoladehyde and rac-glyceraldehyde, pentoses accounted for 60% of the sugars formed with 20% of ribose.
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Zinc–proline catalyzed pathway for the formation of sugars
Chemical communications (Cambridge England), 2004Co-Authors: Jacob Kofoed, Jean-louis Reymond, Miguel Machuqueiro, Tamis DarbreAbstract:Zn-proline catalyzes the aldolisation of unprotected glycolaldehyde in water to give Tetroses and hexoses; threose (33% of the product mixture) was formed with 10% enantiomeric excess of the D-isomer.
Juraj Alfoldi - One of the best experts on this subject based on the ideXlab platform.
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an efficient and versatile synthesis of apiose and some c 1 aldehyde and or 2 3 o protected derivatives
Tetrahedron Letters, 2002Co-Authors: Miroslav Koóš, Bohumil Steiner, Júlia Mičová, Juraj AlfoldiAbstract:Abstract The synthesis of 2,3- O -isopropylidene-β- d -apiofuranose (58% overall yield) from l -arabinose via 3- C -(hydroxymethyl)-2,3- O -isopropylidene- d - glycero -tetrose diethyl dithioacetal is reported. Starting from l -arabinose an alternative precursor of d -apiose, 3- C -(hydroxymethyl)-2,3- O -isopropylidene- d - glycero -tetrose dimethyl acetal, was prepared from 2,3- O -isopropylidene- l - threo -tetrodialdose dimethyl acetal and formaldehyde by the aldol-Cannizzaro reaction. Unprotected d -apiose is accessible from both precursors on acid hydrolysis.
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An efficient and versatile synthesis of apiose and some C-1-aldehyde- and/or 2,3-O-protected derivatives
Tetrahedron Letters, 2002Co-Authors: Miroslav Koóš, Bohumil Steiner, Júlia Mičová, Juraj AlfoldiAbstract:Abstract The synthesis of 2,3- O -isopropylidene-β- d -apiofuranose (58% overall yield) from l -arabinose via 3- C -(hydroxymethyl)-2,3- O -isopropylidene- d - glycero -tetrose diethyl dithioacetal is reported. Starting from l -arabinose an alternative precursor of d -apiose, 3- C -(hydroxymethyl)-2,3- O -isopropylidene- d - glycero -tetrose dimethyl acetal, was prepared from 2,3- O -isopropylidene- l - threo -tetrodialdose dimethyl acetal and formaldehyde by the aldol-Cannizzaro reaction. Unprotected d -apiose is accessible from both precursors on acid hydrolysis.
Steven A. Benner - One of the best experts on this subject based on the ideXlab platform.
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Comment on “The Silicate-Mediated Formose Reaction: Bottom-Up Synthesis of Sugar Silicates”
2016Co-Authors: Hyo-joong Kim, Steven A. BennerAbstract:the formation and stabilization of four- and six-carbon sugars from simple sugars, suggesting a possible prebiotic pathway for the synthesis of biologically important sugars. Here, we show that silicate has minimal impact in these respects, especially when compared to borate minerals. Lambert et al. (1) recently suggested thataqueous sodium silicate mediates aldol re-actions between simple C1 to C3 sugars (formaldehyde, glycolaldehyde, and glyceralde-hyde) to produce Tetroses (C4 sugars) (erythrose and threose) and pentoses (C5 sugars: arabinose, xylose, lyxose, and ribose) and other higher sug-ars. To support their suggestion, they generated product mixtures from these precursor carbohy-drates, both with and without silicate. They then used the differences in the mass spectra of those mixtures to conclude that silicate influenced the relative amounts and stabilities of carbohydrat
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Synthesis of carbohydrates in mineral-guided prebiotic cycles.
Journal of the American Chemical Society, 2011Co-Authors: Hyo-joong Kim, Alonso Ricardo, Heshan I. Illangkoon, Myong Jung Kim, Matthew A. Carrigan, Fabianne Frye, Steven A. BennerAbstract:One present obstacle to the “RNA-first” model for the origin of life is an inability to generate reasonable “hands off” scenarios for the formation of carbohydrates under conditions where they might have survived for reasonable times once formed. Such scenarios would be especially compelling if they deliver pent(ul)oses, five-carbon sugars found in terran genetics, and exclude other carbohydrates (e.g., aldoTetroses) that may also be able to function in genetic systems. Here, we provide detailed chemical analyses of carbohydrate premetabolism, showing how borate, molybdate, and calcium minerals guide the formation of Tetroses (C4H8O4), heptoses (C7H14O7), and pentoses (C5H10O5), including the ribose found in RNA, in “hands off” experiments, starting with formaldehyde and glycolaldehyde. These results show that pent(ul)oses would almost certainly have formed as stable borate complexes on the surface of an early Earth beneath a humid CO2 atmosphere suffering electrical discharge. While aldoTetroses form ext...